Improved incremental bending method and apparatus

Abstract

 Apparatus for forming a bend in sheet material comprises two pivotally mounted jaws (10 and 12) between which is a gap (13) for receiving sheet material (14) which is fed incrementally or indexed through the jaws (10, 12) in the direction of the arrow 15. Rotation of one or other jaw by a controlled amount, together with a controlled extent of incremental feed of the sheet material (14) applies to the sheet material a number of incremental bends which in total form the desired curved profile to be introduced in the sheet material. Other embodiments (Figures 3 and 4) use linearly movable heads to engage the sheet material as the latter is incrementally fed, instead of pivotally movable jaws.

Description

Field of invention

[0001] This invention relates to bending and particularly but not exclusively to bending metal sheet materials. Background to the invention

[0002] It has been proposed to bend elongate articles of relatively low cross-sectional area by longitudinally translating the article and selectively engaging portions of the article with a bending head to form incremental bend portions in which the final configuration of the article is determined by the number and/or angular extent of the incremental bend portions and by the extent of translation between successive incremental bend portions.

[0003] It has also been proposed to provide a machine for bending an elongate article such as a brake pipe in which the machine includes a bend head such as for example a die and former arrangement operable to put a controlled angular extent of bend into a short length of the article and means operable in sequence with operation of the die and former arrangement for advancing the article through the die and former arrangement by a controlled amount to present a further length for bending.

[0004] It is an object of the present invention to apply such method and apparatus to the bending of sheet material and is a particular application to the manufacture of ducts and trunking and in the production of corrugated sheet material.

Summary of the invention

[0005] According to one aspect of the present invention a method of forming a bend in sheet material comprises the steps of incrementally advancing the sheet material between two jaws, effecting relative movement between the two jaws between each said incremental movement so as to introduce a radius of curvature in the sheet material between each said incremental movement.

[0006] According to one aspect of the invention one of the jaws is fixed the other is moveable so that the bending is always in the same direction.

[0007] According to another aspect of this feature of the invention, both of the jaws are moveable but only one jaw is normally moved relative to the other so as to effect bending in either one direction or the other.

[0008] According to a further aspect of the invention, simulataneous movement of both jaws is effected so as to multiply the bending effect.

[0009] According to another aspect of the present invention apparatus for bending sheet material comprises a pair of jaws between which the sheet material can be fed, means for moving at least one of the jaws in a backwards and forwards movement relative to the other jaw so that sheet material located between the two jaws will be bent according to a radius of curvature which is determined by the shape and proximity of the jaws.

[0010] Preferably means is provided for controlling the distance through which the moveable jaw is moved so as to determine the angular extent of the bend introduced into the sheet material

[0011] Preferably means is provided for incrementally advancing the sheet through the jaws between each said movement of one of the jaws relative to the other so that another region of the sheet material can be subjected to bending.

[0012] Preferably means is provided for adjusting the distance through which the sheet material is moved during the said incremental advance.

[0013] It would be appreciated that if only a very small radius of curvature is introduced into the sheet material during each relative movement of the jaws the actual radius of curvature can be to a certain extent controlled by adjusting the distance through which the sheet material is advanced between bends. If the distance moved is very small then a relatively tight bend will be introduced into the sheet material whereas if the distance through which the sheet material is moved is increased then a much shallower bend will be introduced into the sheet material.

[0014] One advantage of apparatus adapted to operate in this way is that varying radius curves and special effects can be introduced into sheet material very easily either by skilled manual operation of the advance mechanism so as to produce the desired shape or more normally by using a shaped cam and follower arrangement so as to determine the distance that the sheet material is moved between bends or by a programmed computer control of the advance mechanism where the program provides the required instructions to the machine to control the advancing mechanism and thereby create the desired curvature according to the specific program .

[0015] The mechanism for advancing the sheet material and for effecting movement of the jaws is conveniently hydraulic although motor driven mechanical means or solenoid operated means or pneumatically operated means may be used.

[0016] According to another feature of this aspect of the invention,-means is provided for moving both of the jaws one in one direction and the other in the other so as to double up the bending effect, means is provided for optionally introducing the movement of the second jaw so as to introduce the"doubling up effect" of the bending effect where particularly tight bends are required.

[0017] As with the means for moving the first jaw, preferably means for moving the second jaw includes means for determining the distance through which the jaw is moved in its backwards and forwards movement so that the actual amount of bend introduced into the sheet material can itself be controlled. However, as previously mentioned, in a preferred arrangement the amount of actual bend introduced is preferably restricted to a very small amount so that the actual radius of curvature introduced into the material can be itself controlled by the distance through which the sheet material is moved between bending operations.

[0018] Each of the jaws conveniently presents a curved surface to the other jaw, the two curved surfaces diverging the one from the other in the direction in which sheet material will move through the jaws.

[0019] The jaws are preferably formed from a suitable material consistent with the surface hardness of the sheet material which is to be bent and typically the jaws are adapted to be removed for replacement cleaning polishing and repair. Conveniently a number of sets of jaws may be provided each pair having a different set of characteristics and the appropriate pair is selected for any particular bending operation of any particular material.

[0020] Conveniently the jaws are elongate members which extend transversely across the path of the sheet material one above and one below the sheet material and themselves extend between 'C' shaped supports each of which pivots about a pivot axis on the other side of the co-operating jaw. Thus the pivot axis for the underside jaw is above the upper jaw whilst the axis pivoting for the upper jaw is below the lower jaw.

[0021] Although the movement of the jaws hitherto has been described in terms of linear movement, it is to be understood that this only applies if the movement is over a small distance and the actual movement of the jaws is in practice around a curved path determined by the distance between the jaw and the pivot axis about which the support members for that jaw are pivoted. In a typical arrangement the radius will be of the order of a few centimetres and it will thus be seen that for a relatively small stroke of a reciprocating mechanism acting on the jaw the resulting movement of the jaw will be around a curved path and in a typical arrangement the stroke of the operating means is such as to produce as much as 45⁰ of rotational movement of a jaw about its axis of pivoting. By the use of stop means or the like, the actual angular extent of this movement can be controlled.

[0022] Typically the means for moving the jaws comprise hydraulic or pneumatic or other linear actuators having a displaceable member relative to a body member such as a cylinder and in which the displaceable member is itself pivotally attached to the jaw which is to move so that linear movement of the displaceable member is converted into a part rotational movement of the jaw around its axis of pivoting.

[0023] It has been found in practice that a preferred bend per bending operation is one which introduces a radius of curvature in the sheet material which lies in the range 2 - 4 times the thickness of the material preferably in the range 2.5 to 3 times the thickness of the material.

[0024] It is to be understood that the invention is not limited to any particular movement of the jaws and the invention encompasses both linear translational movement of the jaws, arcuate movement of the jaws about actual or virtual centres and any combination of linear translational movement and arcuate movement as desired.

[0025] In practice it has been found that when dealing with thin materials and realtively small radii of curvature, a simple linear translating motion of one jaw relative to the other gives a sufficiently accurate approximation if the amount of bending introduced at each incremental advance is restricted, to allow a smooth curve to result in the sheet material from the series of linear translational movements. In such an arrangement the jaws no longer need to move rotationally or even part rotationally but can simply be mounted for pure sliding movement in appropriate guides with the inevitable simpliciation of the moving parts. In such an arrangement the jaws can themselves be acted on directly to form part of the moving members of, for example, hydraulic or pneumatic cylinder and piston arrangements which are angled so that the direction of movement of the moveable member is in the desired direction relative to the sheet material protruding between the jaws so as to produce the desired deflection of the protruding sheet material.

[0026] In a preferred arrangement of the invention, the sheet material is fed between a first pair of fixed jaws which have generally triangular cross-sections and define between opposed faces a parallel channel through which the sheet material will slip whilst their external surfaces define two converging surfaces which serve as guides for two slideable jaws one or both of which can be moved in a generally forward direction to engage the surface of the protruding sheet material and bend the latter around the other protruding jaw which itself may be held stationary or be moved as required.

[0027] The arrangement allows for three different effects:-

(a) if both jaws are moved forward simultaneously and with the same force, the sheet material will be gripped between the two jaws and if each of the jaws is designed to either yield by a controlled distance or can move away from its sliding surface by a controlled distance the result will be that the sheet material gripped between the jaws will be moved in a generally forward direction by a distance determined by the controlled distance through which the jaws yield or themselves move in an outward sense.

(b) If one jaw is held stationary and the other jaw is moved in a generally forward direction it will force the sheet material to deflect into line with the external surface of the fixed jaw member over which the moving jaw is sliding so as to introduce a bend in the sheet material.

(c) If the roles of the two jaws are reversed a bend can be introduced in the opposite direction.

[0028] The radius of curvature introduced into the sheet material can be controlled by the number of simultaneous operations of the two jaws relative to the number of individual bending operations of one jaw provided each incremental advance of the material introduced by the simultaneous operation of the two jaws is sufficiently small.

[0029] Where a corrugated effect is required, then a bend in one direction will be followed by (if required) incremental advance of the sheet material and then by a bend in the opposite direction.

[0030] Sometimes it is desirable that the surface of a sheet material is not only curved but is also embossed or profiled as well. Such profiling or embossing can, of course, be achieved simultaneously with a bending operation by profiling the surface of one or both of the jaws which engage the sheet material.

[0031] The jaws or heads may be movable in an aligned direction which may be substantially perpendicular to the direction of incremental advance of the sheet material. The heads may be mechanically interconnected so as to be movable together, or they may be moved independently under separate control. In either case, one head engages the sheet material to introduce a bend in one direction, and the other head engages the sheet material to introduce a bend in the other direction. By appropriate control of the stroke of movement of the or each head, coupled with control of the degree of incremental movement of the sheet material, a bend of a desired profile can be introduced in the sheet material. The bend can be of any desired radius (within the physical limitations imposed by the machine) and can include a reverse or re-entrant bend.

[0032] The invention has the advantage that sheet material, such as sheet steel, can be taken directly from a coil of the material and fed into the apparatus which may have a shear blade or guillotine to cut the material to desired lengths after bending. This contrasts with known techniques in which sheet material is usually cut to size, squared off before being bent in a press brake.

[0033] The invention will now be described by way of example with reference to the accompanying drawings in which:-

Fig.l is a cross-sectional side view through a pair of jaws adapted to introduce bending in sheet material.

Fig.2 is a perspective illustrative view of a pair of jaws operating to introduce bends in a sheet material workpiece.

Fig.3 is a further cross-sectional side view through a pair of jaws adapted to introduce bending using linear translational movement of the jaws only, and

Fig.4 is a side view of a further embodiment of apparatus for bending sheet materials such as steel.

Detailed description of the drawings

[0034] A pair of jaws or blades 10 and 12 are arranged with a small adjustable clearance between them designated 13. Sheet material 14 is fed in the direction of the arrow 15 by a feeding device (not shown). _The blades are pivoted around axis 17 and 18 and are curved so that each jaw or blade has a radius of curvature struck from the opposite blades pivot axis as a centre. In this way the curved surface of the jaw 10 is formed so as to be a constant radial distance from the axis 17 and the curved surface of the jaw 12 will always be in a constant radial distance from the axis 18.

[0035] As shown in Fig.2, the two hydraulic actuators 19 and 20 are provided for moving the jaws 10 and 12 and are connected to the jaws in such a way as to convert the linear translational movement of the actuators into the arcuate movement of the jaws.

[0036] Operation of actuator 19 causes the jaw 10 to move over the jaw 12 and a curve will be produced in the sheet material 14 protruding between the jaws whose radius is a function of the radius of curvature of the surface of jaw 12 and the radius of curvature of the movement of the jaw 10.

[0037] After the jaw 10 has been returned to its initial position, the sheet material 14 can be incrementally advanced again through the jaws and if the actuator 19 is once again operated, the jaw 10 will once again be moved in a forward direction over the jaw 12 and introduce a further bend in the same direction as the first bend in the sheet material 14.

[0038] By an appropriate combination of linear incremental, advance and bending, any desired radius of curvature can be produced from a minimum radius which is a function of the radius of curvature of the jaws themselves.

[0039] The lower jaw 12 can itself be operated by its own actuator 20 so as to produce bending in the opposite sense to that introduced by movement of the jaw 10. Thus a combination of operations of incremental advance and jaw movement can produce products consisting of sheet material manipulated to various radii in various senses. It will be appreciated that fully sinuous profiles can be produced as well as those consisting of straight sections separated by curved sections.

[0040] Whilst it is envisaged that the invention will normally have jaws which are straight in the direction which is transverse to the feed direction of the sheet material, it is possible that the blades are adapted to maintain a clearance between them and to accept sheet stock material already rolled into say corrugated form.

[0041] By arranging that the means for feeding the sheet material, incrementally advances one lateral edge of the material by a greater distance than the other edge is advanced then, in association with regular bending of the advanced material, so a generally conical form will be produced. If the bending is first in one sense and then the other, the conical form so produced will have a corrugated profile.

[0042] Referring now to Fig.3, it will be seen that if a sufficiently small radius of curvature is introduced and if a sufficiently small incremental advance is permitted between each bending movement, no arcuate movement of the jaws need be provided for and the latter may move in a pure linear translation mode. In Fig.3 two fixed jaws 21 and 22 provide a guide through which sheet material 23 will pass and inclined external surfaces 24 and 25 of the fixed jaws 21 and 22 provide guides over which the flat surfaces 26 and 27 of jaws 28 and 29 respectively can slide. The forward ends of the jaws 28 and 29 are curved at 30 and 31 respectively and movement of one jaw such as 28 over the other jaw such as 29 will produce a bending of the sheet material in the direction shown in the drawing. Movement of the other jaw 29 relatively to the jaw 28 will introduce a bend in the opposite direction

[0043] The minimum radius of curvature will be determined by the radius of the curved sections 30 and 31 of the jaws 28 and 29.

[0044] The jaws 28 and 29 may be accurately guided so that there is no possibility of lateral movement in the direction of the arrows 32 and 33 respectively or alternatively a yielding or actual lateral movement in these directions may be provided for so that simultaneous advance of the jaws 28 and 29 can be used to effect linear advance of the sheet material 23.

[0045] Fig.4 shows a further embodiment of apparatus for bending sheet materials such as steel. In Fig.4 the sheet material to be bent is fed in the direction of arrow C between two rollers 40 and 42 which are biased towards one another (to provide a 'pinch') by a spring 43. The roller 42 is rotatably driven, through a one-way clutch, by a lobe-shaped arm 43. One end 44 of the arm 43 is rounded and is engaged by a member 45 attached to the end of a piston 46 of a hydraulic ram 47. The ram 47 is energised so as to cause the roller 42 to undergo indexing movements which incrementally advance the sheet material in the direction of arrow C, the one-way clutch preventing reverse movement of the sheet material. A helical tension spring 48 acting between the cylinder of the ram 47 and the end 44 of the arm 43 acts to maintain the member 45 in contact with the end 44 of the arm 43.

[0046] The rollers 40 and 42 not only cause incremental advance of the sheet material in the direction of arrow C, but also act to clamp the sheet material between such indexing movements.

[0047] The sheet material is advanced past a reciprocable shear blade or guillotine 49 which co-operates with a stationary counterblade 50. The advancing sheet material is fed horizontally through a gap between stationary guide members 52, 53 and thence into a vertical channel 54. The channel 54 guides two heads 55, 56_'for vertical movement, the two heads being mechanically interconnected by sideplates (not shown) and therefore being movable together in the channel 54 under the control of a hydraulic ram 57. The upper head 55is attached directly to the cylinder of the ram 57, and the lower head 56 carries a bracket 58 which engages the movable element of a linear transducer 59, the latter producing an electrical signal dependent on the position of the heads 55 and 56.

[0048] Each head 55 or 56 has a shaped nose for engaging and bending the sheet material as the latter is indexed in the directioncf arrow C. The radius of curvature applied to the sheet material is dependent on the stroke of the heads 55 and 56 and the incremental advance of the sheet material. The direction of curvature of the bend applied to the sheet material is dependent on which of the heads 55 and 56 engages the sheet material. In the position illustrated in Fig.4 the heads 55 and 56 are in their lowermost extreme position which corresponds to a bend of 90⁰ being applied to the sheet material. Normally, the stroke of the heads applies a bend of smaller angular extent between each of a number of incremental advancing movements of the sheet material.

[0049] Rotation of the arm 43' in the operative direction is limited by a stop 60 which is adjustable.

[0050] After the sheet material has been moved incrementally through the apparatus and the desired bend introduced, the sheet material may be parted by a downwards operative movement of the shear blade or guillotine 49. This is done by rotational movement of an operating lever 62 which is rotated by means of a hydraulic ram 63.

Claims

1. A method of forming a bend in sheet material, comprising the steps of incrementally advancing the sheet material between two movable heads, moving one or both heads between each incremental movement so as to introduce an incremental curvature in the sheet material between each said incremental advance of the sheet material, and repeating the incremental advance and the introduction of the incremental curvature until the combination of the incremental curvatures produces the required bend.

2. A method according to claim 1, wherein the two heads are independently rotatable, one being rotated and the other maintained stationary to bend the sheet material in one direction, and vice versa.

3. A method according to claim 1, wherein the two heads are linearly movable laterally of the direction of incremental advance of the sheet material.

4. A method according to claim 3, wherein the two heads are linearly movable in respective directions which are inclined to the direction of incremental advance of the sheet material, so that movement of either head towards the sheet material effects the incremental advance thereof.

5..- A method according to claim 3, wherein the two heads are linearly movable in an aligned direction perpendicular to the direction of incremental advance of the sheet material.

6. A method according to claim 5, wherein the sheet material is incrementally advanced betweeen two rollers which also act to clamp the sheet material between the incremental advance thereof.

7. Apparatus for bending sheet material, comprising a pair of heads between which the sheet material is fed in an incremental manner, means for moving one or both heads so that the sheet material is bent by the head or heads to a curved profile determined by the amplitude of incremental feed and the extent of movement of the head or heads.

8. Apparatus according to claim 7, wherein the two heads are in the form of jaws which are independently pivotally movable about spaced parallel axes.

9. Apparatus according to claim 7, wherein the two heads are movable along directions substantially equally inclined to the direction of incremental advance of the sheet material, movement of the heads towards the sheet material effecting incremental advance thereof.

10. Apparatus according to claim 7, wherein the two heads are movable along aligned directions substantially perpendicular to the direction of incremental advance of the sheet material, thespparatus addtionally including shearing means for parting a length of sheet material in which a bend has been introduced, and incremental drive means for incrementally advancing the sheet material between the two movable heads.

Drawing